what are verb stems?

Answer 1

Verb stems are the combination of the basic form of a word (called the root) plus any derivational morphemes, but excluding inflectional elements. Since English does not have a lot of verb inflection it is not a concept that is very useful for English verb inflexion, as opposed to German, Greek or Russian conjugation. In most cases the verb stem of English verbs is identical with their infinitive form. Some English verbs just exist in their root form ("must"), others have inflexions for 3rd person singular (to dress - dress-es, to undress [with derivational prefix] - undress-es), for the past tense (dress-ed; undress-ed) and for the continuous form: (dress-ing, undress-ing). In all cases the verb stem is dress- / undress-.